Form, fill and seal packaging machines to form fluid filled containers from a tube of flexible packaging material are known in the art. For example, U.S. Pat. No. 4,747,253 to Schulte discloses an apparatus for the proportion of fluid contents during the manufacture of packing containers. The apparatus includes a filling tube extending into a tube of laminated packaging material to deliver milk into the tube of packaging material. A sealing mechanism below the filling tube forms transverse seals across the tube of packaging material to divide the tube of packaging material into individual cushion-shaped packing containers. Cuts are then formed along the seals to separate the individual packing containers. A gas feed pipe is connected to the filling tube to introduce gas into the tube of packaging material to express air before the individual packing containers are formed so that gas is trapped in each packing container as it is formed. The amount of gas introduced into the tube of packaging material is the same as the volume of the air space provided in the individual packing containers. Unfortunately, gas and/or air in the packing container tends to decrease the product life of the milk introduced into the packing containers.
It has also been considered to use a resistive wire to form transverse seals across a fluid filled tube and cut the tube along the seals simultaneously to separate individual, fluid filled containers from the tube. The ends of the resistive wire are held by pivoting arms which are biased outwardly to apply a longitudinal bias to the resistive wire. In operation, when it is desired to seal and cut the tube, the resistive wire is energized causing the resistive wire to heat rapidly. As the resistive wire heats, it expands. The pivoting arms, which are biased outwardly, take up the slack in the resistive wire thereby maintaining its shape. The resistive wire is then brought into contact with the tube to form a seal across the tube and at the same time cut through the tube along the seal.
Although the above-described prior art methods allow seals to be formed across a fluid filled tube, these methods are only suitable when the seals to be formed across the tube are orthogonal to the longitudinal axis of the tube. In the Schulte method, the sealing and cutting steps are performed at two different stations. However, in situations where seals to be formed across the tube are not orthogonal to the longitudinal axis of the tube, it is important to seal and cut the tube at one station. This is due to the fact that the hydraulic forces acting on the seal by the fluid in the tube above the seal are unevenly distributed along the seal. If the tube is released after the seal is formed, the uneven hydraulic forces tend to move the tube off of its original plane making it difficult to regain control of the tube and subsequently form a cut across the tube along the seal.
Although the resistive wire method allows the tube to be sealed and cut simultaneously, it is also only suitable when orthogonal seals are to be formed across thin film packaging material. This is due to the fact that it is difficult to maintain the shape of the resistive wire and control the pressure required for the resistive wire to seal and cut thicker or laminated packaging material.
An alternative apparatus to form fluid filled containers is disclosed in International Application No. PCT/CA96/00783 published on Jun. 5, 1997 under publication No. WO 97/19852 for an invention entitled “Container With Dispensing Spout And Method For Making Same” and assigned to the assignee of the present invention. Each fluid filled container formed by the apparatus includes a body having an internal reservoir and a narrow, integral dispensing spout extending centrally from the body. The apparatus includes a filling tube extending into a tube of packaging material to deliver fluid into the tube of packaging material. A heat sealing mechanism having upstream and downstream heat sealing bars forms spaced, curvilinear heat seals across the tube of packaging material defining opposite sides of a container. A fluid displacement mechanism in the form of a cylindrical post is associated with each heat sealing bar.
In operation, a heat seal is initially formed at the bottom of the tube of packaging material allowing fluid to be delivered into the tube of packaging material via the filling tube. The fluid level in the tube of packaging material is maintained above the heat sealing bars so that when the curvilinear seals are formed across the tube of packaging material, the resulting containers are filled with fluid and void of air and/or other gasses. Once fluid has been delivered to the tube of packaging material, the fluid displacement mechanism associated with the downstream heat sealing bar is brought into contact with the tube of packaging material to displace fluid upwardly. The downstream heat sealing bar is then brought into contact with the tube of packaging material to form a heat seal thereacross through the fluid in the tube of packaging material. The heat seal is then cut to separate the container from the tube of packaging material.
Thereafter, the fluid displacement mechanism associated with the upstream heat sealing bar is brought into contact with the tube of packaging material to displace fluid upwardly. The upstream heat sealing bar is then brought into contact with the tube of packaging material to form a heat seal thereacross and the heat seal is cut to separate the container from the tube of packaging material. Once this has been done, the tube of packaging material is indexed and the process is performed again to form successive, alternately oriented, interlocked, fluid filled containers. The fluid displacement mechanisms displace sufficient fluid prior to forming the heat seals so that the containers can be made self-supporting and so that the volume of fluid in each container is generally less than or equal to the volume of the reservoir. In this manner, the spouts can be devoid of fluid allowing the spouts to be folded over and releasably attached to the bodies.
European Patent Application No. 99307700.7 published on Apr. 26, 2000 under number 0 995 683 discloses alternative heat sealing and cutting mechanisms for a container forming apparatus. Similar to the apparatus disclosed in International Application No. PCT/CA96/00783, the container forming apparatus includes a filling tube extending into a tube of packaging material to deliver fluid into the tube of packaging material. Heat sealing and cutting mechanisms form spaced, curvilinear heat seals across the tube of packaging material defining opposite sides of a container and then cut the tube along the heat seals to separate individual containers from the tube. Each heat sealing and cutting mechanism includes a carrier supporting a pair of closely spaced heat sealing bands. The carrier also supports a resistive cutting wire centrally disposed between the heat sealing bands. When the carrier is brought into contact with the tube to trap the tube between the carrier and a backing plate, the heat sealing bands are energized to form two closely spaced seals across the tube. After the seals have been formed, the heat sealing bands are de-energized and the resisitive wire is energized to cut the tube between the closely spaced seals.
Although these container forming apparatuses overcome problems associated with conventional container forming apparatuses by forming fluid filled containers devoid of air and/or other gasses, which extends product life, it has been difficult to control precisely the temperature of the heat sealing bars or heat sealing bands to suit the packaging material being sealed. As a result, when dealing with laminated and/or co-extruded multi-layered packaging films, the heat sealing and cutting mechanisms have not yielded high integrity seals consistently over long run cycles. Accordingly, improvements to container forming apparatuses of this nature are sought.
It is therefore an object of the present invention to provide a novel heat sealing and cutting mechanism and container forming apparatus incorporating the same. It is also an object of the present invention to provide a novel heat sealing blade.